The common things we think of certainly apply even in affluent societies.

• Vulnerable populations. Homeless people; the aged and children, pregnancy.
• Chronic alcoholism. Vitamin and caloric deficiency. Liver and pancreatic disease leads to inability to absorb fats, and by extension fat soluble vitamins.
• Acute and chronic illness. Basal metabolic rate accelerates with many illnesses (in burn patients it may actually double). Failure to appreciate the increased nutritional need may compromise recovery.
• Self-imposed dietary restrictions. Body image is preeminent for some people. Anorexia nervosa, bulimia  and other less overt eating disorders affect many people.
• Less common causes. Malabsorption syndromes, genetic defects and drugs that may block the uptake of a particular nutrient.

• An athlete in training will have a much greater caloric need than an otherwise healthy couch potato.
• A patient with emphysema will burn thousands of calories just breathing.
• A person recovering from a severe burn may have twice or even three times the regular caloric need.

So what do you do?